I bought this to climb the mast on my racing yacht. I have since discovered that for a safety inspection we need a hanress or bosun chair that meets a certain standard. Does this hanress meet any recognised international standards I can quote?

BD's harnesses are UIAA and CEN certified... check with the race officials, but it's likely more than adequate. That said, you will need a bosun's chair attachment for longer work sessions. The leg straps won't be very comfortable to sit in for more than a few minutes.

I used to spend a lot of time on boats and I've never heard of any such standards, but I would not be surprised if this harness didn't meet them. Black Diamond is mostly a climbing company, and I would guess that it is not a priority for them to check their products against sailing standards. That said, most climbing harnesses are built more comfortably, lighter, and stronger than any sailing harness I've come across, so if you can convince the inspectors of that, you're golden! Also, I'm not sure how long you'll be in the harness, but be aware that this harness isn't really intended for long hangs. For just a slightly higher price, you can get something like the BD Momentum with padded straps that will be way more comfortable.